•Direct and remote plasma hydrogenation were investigated for the thin film polycrystalline silicon (pc-Si) heterojunction solar cells.•High temperature remote hydrogen plasma facilitates the passivation of defects in pc-Si.•Hydrogenation can induce platelet defects in the sub-surface of pc-Si layer, leading to increased recombination in the space charge region.•Plasma texturing realises defect removal and light trapping at the same time.•8.54% efficiency was achieved using remote hydrogenation at 610 °C and pre-passivation texturing.The hydrogen plasma passivation of thin film polycrystalline silicon (pc-Si) was investigated in conjunction with plasma texturing process to make efficient heterojunction solar cells. The pc-Si layers were first treated using direct and remote hydrogen plasma technologies. The heterojunction solar cells were then fabricated by subsequent deposition of i/n+ a-Si:H. Hydrogenation at high temperature (610 °C) results in enhanced dissolution and diffusion of hydrogen in pc-Si by a factor of about 3 and 4, respectively, in comparison with those at low temperature (420 °C). The hydrogen atoms in the pc-Si layer mainly bond to the silicon dangling bonds and form complexes with dopant atoms. In addition, platelets defects are generated by the hydrogen plasma in the sub-surface region of pc-Si hydrogenated at 420 °C and cause higher saturation current in the space charge region whilst they form in the region deeper than 1 μm at 610 °C. Removal of the platelets using SF6/N2O plasma post-texturing after low-temperature hydrogenation not only enhances the short circuit current but also improves the open circuit voltage and the fill factor simultaneously. Combining plasma pre-texturing with high-temperature hydrogenation, the best 2 µm-thick pc-Si heterojunction solar cell reaches an efficiency of 8.54%.The passivation of thin film polycrystalline silicon solar cells is investigated using direct and remote hydrogen plasma. The relationship between the hydrogen induced defects and the recombination within the space charge region of the heterojunction solar cells is established. Simultaneous enhancement of the voltage and the current and 8.54% efficiency are achieved with synergistic plasma texturing.

•The influence of a-Si:H precursor dehydrogenation on AIC process was studied.•Dehydrogenation can improve microstructural quality of poly-Si thin films.•Smoother surface morphology can be observed on dehydrogenation samples after AIC.•The dehydrogenation process is necessary for fabricating high quality solar cells.Polycrystalline silicon (poly-Si) thin film grown on low cost substrates such as glass at low temperature is an attractive material for cost-effective solar cells. This work studied the influence of dehydrogenation of a-Si:H precursor on the crystallization behavior by aluminum induced crystallization (AIC) process below the eutectic temperature of 577 °C. The a-Si:H films were deposited by PECVD and aluminum was evaporated in a vacuum evaporation equipment, respectively. Some of the a-Si:H thin films were dehydrogenated in nitrogen atmosphere before aluminum evaporation. It was found that hydrogen content in a-Si:H drops to a stable value after annealing at 480 °C for 1 h. Micro-Raman spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction spectroscopy and scanning electron microscopy measurements were used to investigate the structural characteristics of the a-Si:H and the prepared poly-Si thin films. Our results show that although the dehydrogenation increases AIC temperature and reduces AIC rate, it can improve microstructural quality of poly-Si thin films, leading to less tensile stress, higher crystallinity, smoother and more conformal surface morphology.

•AZO thin films were deposited using an in-line high-power/high-throughput direct current magnetron sputtering system.•Low film resistivity and high optical transmission were achieved at processing temperatures below 250 °C.•The oxygen concentration and the film thickness are the major factors impacting the film properties.•The film quality and the sputtering process are suitable for in-line thin c-Si heterojunction solar cell fabrication.The high-power high-throughput direct current (DC) magnetron sputtering of aluminum-doped zinc oxide (AZO) film was investigated for fabricating amorphous silicon/crystalline silicon heterojunction solar cells. The AZO films were deposited using 1.0 wt.% and 2.0 wt.% Al-doped ZnO targets. The functional properties of the deposited films were characterized by measuring the electrical conductivity, Hall mobility, free carrier density and optical transparency. The influence of the sputtering power, oxygen concentration, substrate temperature, post-annealing and film thickness on the film properties were studied systematically. The oxygen in the sputtering gas deteriorates the electrical and optical performance of AZO films, which can be improved by post annealing. An optimal value of 1.0 × 10−3 Ω cm for the resistivity and 90% for the optical transmission was obtained at processing temperatures below 250 °C. Two types of thin Si heterojunction solar cells were prepared and compared using DC sputtered AZO film as the front electrode. Results show that DC sputtered AZO films meet the requirements for use as transparent front electrode in thin Si heterojunction solar cells.